1. Field of the Invention
The invention pertains generally to a motor vehicle door lock such as a side door lock, a rear door lock, a rear hatch lock, or a hood lock and a process for controlling such a motor vehicle door lock.
2. Description of the Related Art
A motor vehicle door lock with the initially mentioned features is known from practice. Such a motor vehicle door lock has an electric motor drive for an assigned actuating or locking element of the motor vehicle door lock. The motor vehicle door lock further includes a sensor for acquiring the position, such as the rotary position, of the drive or the assigned actuating element, and a control means for positioning the drive or the actuating element in a set position and shutting off or short circuiting the drive at a shut-off point which precedes the set position in time and position. The electric motor drive at the shut-off point has a certain energy of motion which leads to a not inconsiderable slowing down, therefore, to further move until the drive, and thus, the actuating element stop. Accurate positioning of the actuating element in the set position is, however, only possible if the actual slowing down is considered when the shutoff point is established. It has been found in practice that the slowing down depends upon various influences such that the positioning accuracy is adversely affected thereby.
An object of the invention is to provide a motor vehicle door lock with an electric motor positioning drive and a process for the control thereof so that accurate positioning under various operating conditions is easily and economically possible.
This object is achieved so that at least one of a start-up characteristic of the drive and a start-up characteristic of the assigned actuating element when the drive is actuated (turned on) is acquired or determined and that at least the start-up characteristic is used to establish a shut-off point which precedes the set position in time and position. Therefore, the start-up behavior of the drive can also be used to draw conclusions about the braking behavior of the drive, thus, without using an additional sensor, enhanced and more accurate characterization of the operating behavior of the drive and its electric motor is possible.
In general, a plurality of different start-up characteristics can be determined. In an exemplary embodiment of the invention, the voltage which is applied to the drive or its electric motor when the drive is actuated is acquired as a first start-up characteristic, at least if it can vary, and at least one of the initial speed, acceleration and values of at least one of the drive and the assigned actuating element which correspond thereto and/or which are derived therefrom is acquired as a second start-up characteristic. It has been found that by means of these start-up characteristics, the required time or positional setting of the shut-off point in advance of the set position which is to be assumed in the shut-off state can be established or determined. This is explained by the fact that from the two indicated start-up characteristics, the temperature of the drive, which has a major effect upon its braking and shut-off behavior, can be estimated or approximately determined using these start-up characteristics. Accordingly, depending upon the estimated temperature or the aforementioned start-up characteristics, the advanced positioning of the shut-off point which is necessary for accurate positioning can be ascertained.
Other details, features, objectives and advantages of this invention are detailed below using the drawings of one preferred embodiment.